The present invention relates to a system and method for communicating multiple broadcast messages over a telecommunications system to a plurality of subscriber terminals and in particular to a system and method that allows the broadcasting of multiple streams of information to a plurality of wireless portable terminals. The system is particularly but not essentially based on the Digital Enhanced Telecommunications (DECT) standard.
It is known to provide telecommunications systems with an audio broadcast facility of some type, depending on the requirements and the capability of the particular system. The message that is broadcast may then be received by a plurality of the system users. One basic system is noted in the English language abstract of Japanese patent application number JP-A-5-48684. The abstract relates to a cordless telephone set having a telephone master set provided with a voice recording part, a radio (transmitting) part and antenna. A plurality of slave sets are provided with an antenna, radio part, an amplifier and a speaker. A recorded voice message may then be transmitted from the master set to the slave sets.
With such an arrangement, if each slave set is provided with only a simple receiver section (radio part), the receiver section may then be required to support not only reception of the broadcast but also support the exchange of normal telephone traffic with the master set. Problems can arise if a slave set is already being used for conducting a telephone conversation. Further problems may be experienced when attempting to transmit a broadcast to particular slave sets. No mention is made of any facility for broadcasting multiple messages.
Another approach to providing an audio broadcast facility to a plurality of terminals in a telecommunications system is for a base station or some other type of control unit to set up a telecommunications link with each terminal of the plurality in a manner that is conventional for the system, that is, the type of link that is used to carry voice or data file traffic. The audio message is then broadcast by sending it over each of the links simultaneously in the same manner that the voice signal of a normal telephone conversation would be carried. Since an individual point-to-point link needs to be established with each terminal simultaneously, this can place a heavy, if not impossible demand on the system which may only be provided with resources sufficient to establish calls to a limited number of terminals at a given time. The problem may be alleviated to some extent by setting up calls to individual terminals of the plurality one by one, or to fractions of the total number of the terminals sequentially, although this will lead to a delay while a broadcast is made to each of the terminals (or fractions of the total number of terminals) for which the broadcast is intended. This may be unacceptable in certain situations and applications, especially if the welfare of personnel using the terminals is somewhat dependant on timely reception of the broadcasts.
In telecommunications systems employing wireless links to portable terminals, attempting to provide a broadcast (such as an audio broadcast) by establishing such traffic calls to a large number of portable terminals simultaneously is even more difficult. This is partly due to the limited number of channels that may be handled by a single base station and the amount of radio spectrum that has been allocated for use by such telecommunication systems. An example of one such system is a DECT compliant telecommunications system (DECT is an abbreviation for Digital Enhanced Cordless Telecommunications). DECT systems are described in the standard ETS 300 175 of which there are several parts. The standard is published by the European Telecommunication Standards Institute and is incorporated herein by reference.
In a DECT compliant telecommunications system the portable terminal is called the portable part (PP) and the fixed terminal is called the fixed part (FP). The fixed part includes at least one radio fixed part (RFP) which is a radio termination (or radio end point) for communication with the portable part. In this case performing a broadcast call to a number of portable parts by setting up an ordinary voice or data carrying channel (known in DECT as a traffic bearer) to each portable part (PP) would quickly exhaust system capacity and overload system resources. This would result in the inability to broadcast to more than just a few PP""s and even the failure to maintain or establish normal voice or data communications to PP""s while the broadcast occurs. If such a system is required to convey multiple broadcast messages then system capacity may be exhausted in the same way.
It is an object of the present invention to provide a system for the broadcasting of multiple, simultaneous messages such as audio messages or data files over a telecommunications system that allows a plurality of portable terminals to receive at least one of the messages that are broadcast.
It is another object of the present invention to provide a system for the broadcasting of multiple, simultaneous messages such as audio messages or data files over a telecommunications system and which allows a plurality of portable terminals to receive at least one of the messages that are broadcast, while at the same time making efficient use of system resources.
In accordance with a first aspect of the present invention there is provided a broadcast system for communicating multiple at least partially overlapping broadcast messages in a telecommunications system having at least one fixed terminal for communication with one or more portable terminals, said broadcast system including:
first transmitter means for transmitting first messages from the or each fixed terminal, each message including information specifying a channel, selected for that fixed terminal, to convey one of the broadcast messages;
control means responsive to the first messages for individually causing the or each portable terminal to receive on at least one of the specified broadcast message channels; and
second transmitter means for transmitting from the fixed terminal the broadcast messages on the said specified broadcast message channels for reproduction of at least one of the broadcast messages by the or each portable terminal.
The broadcast messages are typically audio or data file type messages.
The first and second transmitter means may be incorporated in the fixed terminal. Indeed the first and second transmitter means may be the same entity. The first and second transmitter means may be the same system component. The control means may be located in the portable terminal. Each of the first and second transmitter means and control means may be system applications or the like and the terms do not necessarily relate to hardware.
By broadcasting the messages as connectionless messages it is possible to transmit each message to a plurality of portable terminals without setting up an individual call to each portable terminal and therefore without exceeding the limitations of the system. Since each broadcast message may be transmitted independently of other broadcast messages the broadcasts can occur at the same time if so required.
Such a broadcast facility would be of particular use where portable terminals are being carried by security guards or medical workers, where quick substantially simultaneous broadcasting of messages or an alarm signal to personnel is important.
The broadcast system can be based on a modified form of the DECT standard. In this case the specified broadcast channels may be DECT physical channels, each of which may then be used to support a DECT simplex bearer. Each specified channel can be used to support a connectionless downlink bearer. By providing a broadcast system in the form of a modified DECT system, there are particular advantages to be gained, as the applicants have recognised, since the DECT standard allows for connectionless communications to be set up from the radio fixed parts of the fixed terminals to the portable parts although these connectionless communications are normally only used to carry system information and other control information. Although basic, known, unmodified DECT portable parts will not be able to receive the broadcast messages, their normal operation within the telecommunications system will be unaffected.
Furthermore, if the telecommunications system is based on a modified form of DECT compliant telecommunications system, the first messages may be transmitted as short page messages.
The broadcast system may further include:
means for assigning each portable terminal with a broadcast group identity; and
means for including broadcast group identity information in each first message,
wherein the control means causes the or each portable terminal to receive on one or more of the specified broadcast channels only if the said portable terminal has an assigned broadcast group identity that corresponds to the broadcast group identity transmitted in the first message for the one or more specified broadcast channel.
This allows only specific portable terminals to be selected for receiving particular broadcast messages. This may be advantageous for calling only certain groups of portable terminals, for example portable terminals carried by people who belong to a particular organisational department or who belong to a particular management level.
The broadcast system may also include means for periodic transmission of each first message for the duration of it""s associated broadcast message to allow portable terminals to roam into geographical areas covered by a different fixed terminal and to receive broadcasts from the different fixed terminal even if this requires the roaming portable terminal to receive a broadcast message on a different specified channel and to change the specified channel that it receives on. This offers the obvious advantage of not restricting a user of a mobile terminal to be in the radio coverage area of a particular fixed terminal in order to continue to receive the broadcast message.
In accordance with a second aspect of the present invention there is provided a method for communicating multiple at least partially overlapping broadcast messages in a telecommunications system having at least one fixed terminal for communication with one or more portable terminals, said method comprising the steps of:
transmitting first messages from the or each fixed terminal, each message including information specifying a channel, selected for that fixed terminal, to convey one of the broadcast messages;
individually causing the or each portable terminal to receive on at least one of the specified broadcast message channels; and
transmitting from the fixed terminal the broadcast messages on the said specified broadcast message channels for reproduction of at least one of the broadcast messages by the or each portable terminal.
In accordance with a further aspect of the present invention there is provided a communications device apparatus having the technical features of the first transmitter means in the broadcast message system.
In accordance with a yet further aspect of the present invention there is provided a communications device apparatus having the technical features of the control means in the broadcast message system.
In accordance with a yet further aspect of the present invention there is provided a communications device apparatus having the technical features of the second transmitter means in the broadcast message system.
Other aspects and optional features of the present invention appear in the appended claims, to which reference should now be made and the disclosure of which is incorporated herein by reference.